JPH04126489A - Brightness/chromaticity separating circuit of composite picture signal - Google Patents

Abstract

PURPOSE: To always accurately separate luminance signals and chromaticity signals from each other by constituting three line separation filters which can adapt themselves to vertical luminance changes and selecting an output signal by comparing the signal of the present line with the signals of the preceding and succeeding adjacent lines. CONSTITUTION: Composite video signals CV are successively outputted with one-line delay by means of one-line delaying devices 11a and 11b and the signals CV and the output signal of the delaying device 11b are respectively inverted by means of inverter gates 12a and 12b. The output signals of the gates 12a and 12b are respectively impressed upon the terminals (a) and (c) of a selector 18 after the output signal of the delaying device 11a is added to the signals at adders 13a and 13b. DC components are removed from the signals outputted from the selector 18 while the signals are passed through a band-pass filter 19 and only chromaticity signals C are separately outputted from the filter 19. In addition, since a subtractor 16c subtracts the chromaticity signals C form the output signal of the delaying device 11a, only luminance signals are separately outputted from the subtractor 16c.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a processing circuit for a color television composite video signal of the NTSC system.
A luminance/chromaticity signal that selectively uses the output signal of the MB Filter to accurately separate the luminance signal and chromaticity signal.
This invention relates to a chromaticity signal separation circuit. [0002]

[Conventional technology]

Conventionally, in a luminance/chromaticity signal separation circuit for a composite video signal, as shown in FIG.
A multiplier 4 that multiplies the output signals of the line delay device 1a to IC.
a to 4C the composite video signal Cv and the 1-line delay device 1a
multipliers 4d to 4h that multiply the output signals of ~1d, respectively;
Those multipliers (4a to 4c) (4f to 4h) (
an adder 2a that adds the output signals of 4d to 4f), respectively;
2b, 2c, inverter gates 3a, 3b for inverting the output signals of the adders 2b, 2c, and the one-line delayers 1b to 1d using the composite video signal Cv and the output signals of the one-line delayers 1a, lb. subtracters 58 to 5C that respectively subtract the output signals of the subtractors 5a to 5C;
A minimum value detector 6 detects the minimum signal among the output signals of and outputs it as a selection control signal, and according to the selection control signal of the minimum value detector 6, the output signal of the adder 2a and the output of the inverter gates 3a, 3b are detected. a selector 7 that selects and outputs a signal; a bandpass filter 8 that removes a DC component from the output signal of the selector 7 and outputs it as a chromaticity signal C; The operation of such a conventional luminance/chromaticity signal separation circuit for a composite video signal will be explained as follows. [0003] That is, the composite video signal Cv is sequentially delayed by one line in one line delayers 1a to 1d and outputted, and the output signals of the one line delayers 1a to 1c are outputted by -1/1 in multipliers 4a to 4c, respectively.
4.1/2. After being multiplied by -174, the adder 2a adds the signals and applies them to the terminal a of the selector 7. Next, the output signals of the one-line delay devices 1b to 1d are processed by multipliers 4f to 4h, respectively.
1/4.1/2. After being multiplied by -1/4, the signals are added by an adder 2b, and the output signal of the adder 2b is inverted by an inverter gate 3a and then applied to a terminal of a selector 7. and the composite video signal Cv and the 1-line delay device 1a,
The output signal of lb is -1/4.1 in multipliers 4d to 4f, respectively.
/2. After being multiplied by -1/4, the signals are added by an adder 2c, and the output signal of the adder 2c is inverted by an inverter gate 3b and then applied to the terminal C of the selector 7. On the other hand, the composite video signal Cv is applied to the post/IX value detector 6 where it is subtracted from the output signal of the 1-line delay device 1b by the subtracter 5a, and 1
The output signals of line delay devices 1a and lb are also subtracted by subtractor 5a,
After being subtracted from the output signals of the one-line delay devices 1c and ld at step 5c, the signals are applied to the minimum value detector 6. Therefore, in the maximum tJz value detector 6, the subtracters 5a to 5c
A signal with a small value in the middle of the output signal is detected and output as a selection control signal, and one signal among the output signals of the adder 2a and the inverter gates 3a, 3b is selected by the selector 7 according to the selection control signal. The signal selected by the selector 7 passes through a bandpass filter 8 to remove the DC component, and then is output as a chromaticity signal C, which is then passed through the one-line delay unit 1b.
The output signal is subtracted from the chromaticity signal C by a subtracter 9 and output as a luminance signal Y. Here, the composite video signal of the NTSC system has a pattern in which the chrominance signal is carrier suppressed modulated on the chrominance subcarrier signal and added to the luminance signal, and the phase of the chrominance subcarrier is 180° difference between adjacent inputs. It comes to have. [0004]

[Problem to be solved by the invention]

However, in such conventional luminance/chromaticity signal separation circuits for composite video signals, the luminance signal and chromaticity signal are separated using the characteristics of the composite video signal and the correlation between adjacent lines. However, when a change in brightness appears vertically, there is no correlation between adjacent lines, so the brightness signal and chromaticity signal cannot be accurately separated, and when the degree of change in the brightness signal is small, However, since the luminance signal and chromaticity signal cannot be separated accurately and a large number of one-line delay devices are used, the structure is complicated. [0005] Therefore, as a result of repeated research in order to solve such problems, the present inventors have attempted to provide the following luminance and seven chromaticity signal separation circuit for a composite video signal.[000
6]

Means and Effects for Solving the Problems That is, it is an object of the present invention to provide a signal that can be applied even when the change in the luminance signal in the vertical direction is minute. j (O) An object of the present invention is to provide a luminance/chromaticity signal separation circuit for a composite video signal that can accurately separate luminance signals and chromaticity signals. Another object of the present invention is to accurately separate a luminance signal and a chromaticity signal using a simple structure luminance/chromaticity signal separation circuit for a composite video signal using two 1-line delay devices. This is what I am trying to do. [0007]An object of the present invention is to configure three line separation filters that adapt to vertical luminance changes using two 1-line delay devices, and to separate the current line signal from the previous one.
After comparing the signals of the adjacent lines, if the luminance difference is above a certain value, select the output signal of the line separation filter with which the luminance difference appears smaller.The luminance signal and chromaticity signal are then separated, and the luminance difference is kept constant. This is achieved by selecting the output signal of the line separation filter using both of the two one-line delay devices when the value is less than the value, and then separating the luminance signal and the chrominance signal. [0008]

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram for separating luminance/chromaticity signals of a composite video signal according to the present invention, and as shown in the drawing, the composite video signal Cv
1-line delay device 11a that sequentially delays 1 horizontal line.
, 11b, and an inverter gate 1 for inverting the composite video signal C and the output signal of the one-line delay device 11b.
2a, 12b, and the inverter gate 12a,
Adders 13a and 13b add the output signal of the one-line delay device 11a to the output signal of the inverter gate 12b, respectively, the output signal of the inverter gate 12a, the output signal of the one-line delay device 11a, and the output signal of the inverter gate 12b Multipliers 14a, 14b, 14c that multiply 1/4.1/2.1/4, respectively, and the multipliers 14a to 1
4c; and low-pass filters 15a, 15b, and 15c that pass the base of the low frequency signal in the composite video signal C and the output signals of the one-line delay devices 11a and 11b, respectively. , a subtracter 16a that subtracts the output signal of the low-pass filter 15b from the output signal of the low-pass filters 15a and 15c, respectively.
, 16b and the subtractor 16a. Multipliers 14d and 14e that multiply the output signal of 16b by 1/4.1/4, and a comparator 1 that compares the magnitudes of the output signals of the multipliers 14d and 14e and outputs a selection control signal.
7 and the adder 1 according to the selection control signal of the comparator 17.
A selector 18 selects and outputs the output signals of 3a, 13b, and 13c, and removes a DC component from the output signal of the selector 18, passes only a 3.58 MHz color width carrier wave signal, and outputs it as a chromaticity signal C. A luminance/chromaticity signal separation circuit for a composite video signal according to the present invention is constructed by a bandpass filter 19 and a subtracter 16c that subtracts the chromaticity signal C with the output signal of the line delay device 11a and outputs it as a luminance signal Y. It is configured. [0009] The operation of the luminance/chromaticity branching circuit for composite video signals according to the present invention configured as described above will be explained as follows. The composite video signal Cv is sequentially delayed by one line in the one-line delay devices 11a and 11b and output.
The output signal of the 1-line delay device 11b is inverted by the inverter gate surfaces a and 12b, respectively, and the inverter gate)
The output signals of 12a and 12b are converted to 1 by adders 13a and 13b.
After being added to the output signal of the line delay device 11a, the signals are applied to terminals a and c of the selector 18. and the inverter gate 12a, the 1-line delay device 11a, and the inverter gate) 12b(7) The output signal is sent to the multipliers 14a and 14.
The signals are multiplied by 1/4.1/2.1/4 in b and 14c, respectively, and then added in an adder 13c, and the output signal of the adder 13c is applied to a terminal of a selector 18. On the other hand, in the composite video signal Cv and the output signals of the 1-line delay devices 11a and 11b,
The high frequency signal of the chromaticity signal component is passed through a low pass filter 15a.
, 15b, 15c, only the low frequency signal of the luminance component can pass through the low pass filters 15a, 15b, 15c.
pass through. Therefore, at this time, the low-pass filter 1
The output signals of 5a, 15b, and 15c are signals representing the luminance levels of three vertically continuous pixels (PIXel). In this way, the signals output from the low-pass filters 15a and 15c are subtracted from the signal output from the low-pass filter 15b by the subtracters 16a and 16b, respectively. Therefore, if the output signal of the 1-line delay device 11a is assumed to be the signal of the current line, the luminance difference signal between the current line and the previous line is the subtracter 1
6b, a luminance difference signal between the current line and the subsequent line is outputted from the subtracter 16a, and is outputted from the subtractor 16a, 16b.
c7) The output signal is 1/4 in multipliers 14d and '14e, respectively.
．． Multiplied by 1/4. Multiplying by 174 here results in eliminating the two least significant bits in the input signal database. As mentioned above, the multipliers 14d, 14
The comparator 17 compares the magnitudes of the signals output at e, and three types of selection control signals are output and applied to the selector 18 according to the comparison results. That is, when the magnitude of the output signal of the multiplier 14d is smaller than the magnitude of the output signal of the multiplier 14e by a certain value (for example, 3), conversely, the magnitude of the output signal of the multiplier 14e is smaller than the magnitude of the output signal of the multiplier 14d. A selection control signal is outputted from the comparator 17 and applied to the selector 18 when the magnitude is smaller than the magnitude by a certain value or more and when the difference in magnitude between the output signals of the multipliers 14d and 14e is equal to or less than a constant value,
Therefore, in the selector 18, the terminals a, b, c,
The signal with the smaller luminance difference among the signals applied to is selected and output. For example, as described above, if the magnitude of the output signal of the multiplier 14d is smaller than the thickness of the output signal of the multiplier 14e by a certain value or more, the selector 18 selects the output signal of the adder 13a to be applied to the terminal a. If the magnitude of the output signal of the multiplier 14e is smaller than the magnitude of the output signal of the multiplier 14d by a certain value or more, the selector 18 selects the output signal of the adder 13b to be added to the terminal C. If the difference in magnitude between the output signals of the multipliers 14d and 14e is less than a certain value, the selector 18 selects and outputs the output signal of the adder 13C to be added to the terminal. Ru. In this way, the signal output from the selector 18 passes through the band pass filter 19, and the DC component is removed.
．． Only the chromaticity signal C, which is a signal close to 58 MHz, is separated and output. At this time, the subtracter 16c subtracts the chromaticity signal C from the output signal of the one-line delay device 11a, so that the subtracter 16c separates and outputs the luminance signal. [0010]

【Effect of the invention】

As described above, in the luminance/chromaticity signal separation circuit for a composite video signal according to the present invention, two 1-line delay devices are used to configure three line separation filters that adapt to luminance changes in the vertical direction. This has the effect of providing a circuit with a simple structure that solves the problem of reduced correlation between adjacent lines in conventional line separation filters. Furthermore, even when the brightness changes in the vertical direction are subtle, the output signal of the line separation filter using both two 1-line delay devices can be selected to accurately separate the brightness signal and chromaticity signal. be.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram for separating luminance and seven chromaticity signals of a composite video signal according to the present invention.

[Figure 2] FIG. 2 is a circuit diagram for separating luminance/chromaticity signals of a conventional composite video signal.

[Explanation of symbols]

la, 11b...1 line delay device 2a, 12b...inverter gate 3a to 13c...
... Adders 4a to 14e... Multipliers 5a to 15c... Low pass filters 6a to 16c.
...Subtractor 7...Comparator 8...Selector 9...Band pass filter

[Document core]

drawing

[Figure 1]

Claims (2)

[Claims] 1. A one-line delay unit (11a, 11b) that sequentially delays a composite video signal by one horizontal line, and an inverter gate (12a, 11b) that inverts the composite video signal and the output signal of the one-line delay unit (11b). 12b), adders (13a, 13b) that add the output signals of the 1-line delay device (11a) to the output signals of the inverter gates (12a, 12b), respectively;
12a), multipliers (14a, 14b, 14c) that multiply the output signals of the 1-line delay device (11a) and the inverter gate (12b) by predetermined values, respectively, and the output signals of the multipliers (14a to 14c); Adder (13
c), the composite video signal and the 1-line delay device (1
Low-pass filters (15a, 15b, 15c) that pass only low-frequency signals in the output signals of 1a, 11b), respectively.
and subtracters (16a), (16b) for subtracting the output signal of the low-pass filter (15b) from the output signal of the low-pass filter (15a, 15c), respectively; multipliers (14d, 14e) that multiply the output signals of 16b) by predetermined values, respectively;
a comparator (17) that compares the magnitude of the output signal of the adder (14e) and outputs it as a selection control signal; Selector (18) that selects and outputs one signal
), and a bandpass filter (19) that removes the DC component from the output signal of the selector (18) and passes only the chromaticity signal.
and a subtracter (16c) that subtracts the chromaticity signal with the output signal of the 1-line delay device (11a) and outputs a luminance signal.
A luminance/chromaticity signal separation circuit for a composite video signal. 2. The comparator (17) includes the multiplier (14).
When the magnitude of the output signal of d) is smaller than the magnitude of the output signal of the multiplier (14e) by a certain value or more, or if it is larger than the magnitude of the output signal by a certain value or more, and the multipliers (14d) and (14e)
2. The luminance/chromaticity signal separation circuit for a composite video signal according to claim 1, wherein the circuit is configured to output three types of selection control signals depending on the case where the difference in magnitude of the output signals is less than a certain value.